I think it all depends on what you are going for.
If you are going for a tidepool look and want to look down on your tank, then go with the 24x24x12.
If you want to view mostly from the side then go with the Oceanic. The 150watt MH might not allow you to keep high light anemones in the Oceanic, if that was what you were going for.
Personally, If you are going to have a tank built, I would go with a 24x24x16. That would give you the best of both worlds. A 12" high tank is great for a frag tank, but not very good for side viewing.